Just as Freudians have a sort of built-in defence against any criticism, if you disagree with a Freudian he says, 'Oh, that's all because you saw something nasty in the woodshed when you were a child,' and it dismisses your arguments as being irrational. The Marxists dismissed evidence against their beliefs on the grounds that this was all capitalist propaganda. I know this, to you, will sound absurd, and to me, it sounds absurd today, but we, my contemporaries, knew of the stories about the purges, about the excesses of Stalinism, not what is known now but we knew that such stories existed, but we dismissed them on the grounds that that's the kind of thing you'd expect the capitalist press to say. We didn't believe them. And we were wrong not to believe them, but we didn't. We had a coherent world view, which fitted together, which explained things, and which was... enabled us to ignore those facts which didn't fit. And... let me go on about the Communist thing a bit further because it was important in my earlier days as a scientist, also. When I... I... I mean I was active in the Communist Party during my period as an engineer, although I was also working very hard as an aircraft engineer and I was also being a Communist. But the thing that ultimately undermined my... my faith, if you like, and in a sense it was like being a member of a religious movement I think, if I'm honest, really it was the Lysenko Affair. And people have sometimes said to me, 'For goodness sake, why swallow the Gulags and start getting fussed about a few geneticists being put in prison and some errors in science?' The difference was, that what I knew about the Lysenko business was said by the Russians themselves, it wasn't something I could dismiss as capitalist propaganda, it was something that the Russians were publishing. I can remember to this day reading the 1948 book about the proceedings of the Lenin Academy of Agricultural Sciences or something, and being absolutely horrified.

[Q] The Situation in Biological Science Today.

That's right, yes. I mean, I couldn't dismiss that as capitalist propaganda, it was socialist propaganda, if you like. And this forced me to reconsider my position on all sorts of other questions. If they're as wrong as they are about that, how many other things are they wrong about? I didn't actually leave the Communist Party until 1956, when the... during the Hungary business. But I had really lost all conviction in my Communist faith by '48, '49. But there is a sort of loyalty. It's difficult to know whether to call it a reluctance to admit one has been that wrong, which is a not very honourable attitude. And... but there was an element of loyalty about it. It's very easy to... well, no, let me say that again. It is very hard to leave a beleaguered group of people. I mean, the Communist Party was increasingly beleaguered - attacked - an increasingly... a minority despised by society during that period. It's very hard to leave, you feel you're like a rat leaving a sinking ship, you know, leaving your friends. And so I just sort of sat there, not doing anything for the Communist Party, not really believing in what it was saying a lot of the time, but reluctant actually to leave.

The late British biologist John Maynard Smith (1920-2004) is famous for applying game theory to the study of natural selection. At Eton College, inspired by the work of old Etonian JBS Haldane, Maynard Smith developed an interest in Darwinian evolutionary theory and mathematics. Then he entered University College London (UCL) to study fruit fly genetics under Haldane. In 1973 Maynard Smith formalised a central concept in game theory called the evolutionarily stable strategy (ESS). His ideas, presented in books such as 'Evolution and the Theory of Games', were enormously influential and led to a more rigorous scientific analysis and understanding of interactions between living things.

Richard Dawkins was educated at Oxford University and has taught zoology at the universities of California and Oxford. He is a fellow of New College, Oxford and the Charles Simonyi Professor of the Public Understanding of Science at Oxford University. Dawkins is one of the leading thinkers in modern evolutionary biology. He is also one of the best read and most popular writers on the subject: his books about evolution and science include "The Selfish Gene", "The Extended Phenotype", "The Blind Watchmaker", "River Out of Eden", "Climbing Mount Improbable", and most recently, "Unweaving the Rainbow".